It is the primary purpose of this research grant to extend and refine the previous work in cognitive development to include not only classification, but the cognitive processes of seriation and conservation as well. Specifically the following six objectives have been set forth. First, developmental taxonomies for the three areas will be developed and/or refined. Second, diagnostic insturments capable of assessing the attainment of children's abilities at any given stage of development will be developed and refined based upon psychometrically and conceptually sound dependent measures and an empirically determined evaluation of the parameters of age, sex and socio-cultural experience. Third, the validity of Gagne's cumulative learning model will be tested on various terminal objectives, and based upon these results, two additional objectives can be achieved. That is, the empirical interrelationships of the three cognitive processes will be determined, and effective training programs which adapt to a child's stage of development and which provide not only for learning but for optimal transfer as well will be developed and/or refined. Finally, methods of economically and efficiently presenting these diagnostic-prescriptive training programs to large numbers of children in the classroom setting will be developed and used as curriculum models for other programs.